Photographic supersensitized silver halide emulsions

ABSTRACT

A photographic silver halide emulsion containing at least one carbocyanine dye represented by the general formula:   AND AT LEAST ONE CARBOCYANINE DYE REPRESENTED BY THE GENERAL FORMULA:   The various individual moieties indicated in the above identified structures are defined in the specification.

United States Patent Inventors Keisuke Shiba; 1

Akira Sato, both of Mlnami-Ashigara Machi, Japan July 17, 1968 Dec. 21, 1971 Full Shashln Film Kabushlkl Kalsha Kanagawa, Japan July 17, 1967 Japan Appl. No. Filed Patented Assignee Priority PHOTOGRAPHIC SUPERSENSITIZED SILVER l'lALlDE EMULSIONS 3 Claims, No Drawings Int. Cl Field of Search References Cited UNITED STATES PATENTS 7/1942 Wilmanns et al. 1/l968 Jones et al.

Primary Examiner.l. Travis Brown Attorney-Sughrue, Rothwell, Mion, Zinn and Macpeak ABSTRACT: A photographic silver halide emulsion containing at least one carbocyanine dye represented by the general formula:

PIIOTOGRAPHIC SUPERSENSITIZED SILVER I'IALIDE EMULSIONS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a photographic silver halide emulsion which has been spectrally sensitized, and more particularly, to a photographic silver halide emulsion having high spectral sensitivity in the green region.

2. Description of the Prior Art One technique for preparing photographic silver halide emulsions which has been employed in the past involves a spectral sensitizing method, i.e., a method in which by incorporating a sensitizing dye in a photographic silver halide emulsion, the sensitive region of the silver halide emulsion is extended to a longer wave length side. The spectral sensitivity of a photographic silver halide emulsion generally depends upon the chemical structure of sensitizing dyes which are incroporated therein and the properties of the silver halide emulsion, such as the composition, crystal habits, crystal surface characteristics of the silver ion concentration, and the pH of the silver halide emulsion. In addition, additives, such as stabilizers, antifoggants, wetting agents, hardening agents, couplers, and the like, are commonly used to alter the characteristics of the silver halide emulsion. In general, the presence of additives in a photographic silver halide emulsion will reduce the spectral sensitivity of the silver halide emulsion.

When it is desired to produce a spectral sensitivity to a definite wave length region, two or more sensitizing dyes are usually employed, but the spectral sensitivity obtained by combinations of two or more sensitizing dyes is usually lower than that obtained when using a single sensitizing dye. This phenomenon is known as antisensitization.

It has been found that in certain specific cases, the chemical structures of two sensitizing dyes form a synergistic combination wherein the spectral sensitivity of a treated silver halide emulsion is extraordinarily increased in comparison to the use of the sensitizing dyes independently. This phenomenon is known as super-sensitization." It is thus very important in the field of spectral sensitization to find a proper and specific combination of two or more sensitizing dyes which will yield a super-sensitization effect.

A photographic light-sensitive element is, in general, required to have a spectral sensitivity over the visible wave length region and, in particular, to have highest spectral sensitivity at a green sensitive region, since this is the highest visible light sensitive region from the view point of color or tone reproduction.

SUMMARY OF THE INVENTION It has been found that a photographic silver halide emulsion having an extremely high spectral sensitivity may be obtained by the addition thereto of at least one carbocyanine dye represented by the general formula:

and at least one carbocyanine dye represented by the following general formula:

With respect to the dye represented by general formula 1 above, Y, and Y, each represent a member selected from the group consisting of a hydrogen atom and a halogen atom; Y, and Y at least one of which may be substituted by a group other than a hydrogen atom, each represent a member selected from the group consisting of a hydrogen atom, an alkyl group, a halogen atom, and an alkoxy group; R,, R,, and R, each represent a member selected from the group consisting of an alkyl group, a substituted alkyl group, and an aryl group; R, represents a member selected from the group consisting of a hydrogen atom, an alkyl group, and a group which together with R, or R, forms an alkylene linkage; X," represents an anion; and p represents 0 or I; said dye forming an intennolecular salt when p is 0.

With respect to the carbocyanine dye represented by general formula II above, R, and R,, each represent a member selected from the group consisting of an alkyl group, a substituted alkyl group, and an aryl group; R represents a member selected from the group consisting of a hydrogen atom, a methyl group, and an ethyl group; Z, and Z, represent nonmetallic atoms necessary for completing a nucleus selected from the group consisting of a benzoxazole nucleus, a

naphthoxazole nucleus, a benzothiazole nucleus, a thiazole nucleus, a benzimidazole nucleus, a naphthoimidazole nucleus, a benzselenazole nucleus and a selonazole nucleus; X, represents an anion; and q represents 0 or I; said dye forming an intramolecular salt when q is 0.

It has been found that when combinations of the two carbocyanine dyes represented above are utilized as additives to a photographic silver halide emulsion, that a highly sensitive emulsion will result. The super-sensitization which may be obtained has no hannful effect on the spectral sensitivity in the red spectral regions and, upon proper selection of the carbocyanine dyes, an extremely high green-sensitive spectral sensitivity will be obtained.

If desired, by using the carbocyanine dye represented by general formula I together with the carbocyanine dye represented by general formula II, the green sensitivity can be increased while shifting the maximum sensitizing wave length.

An object of the present invention is thus to provide a photographic silver halide emulsion having a higher green sensitive spectral sensitivity by super-sensitization, without reducing the spectral sensitivity at a red sensitive region (hereinafter, this sensitivity will be called "red sensitivity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS By incorporating in a photographic silver halide emulsion at least one carbocyanine dye represented by the general formula I i s (Xr')v wherein Y, and Y each represents a hydrogen atom or a halogen atom; Y, and Y, each represents a hydrogen atom, a halogen atom, an alkyl group, or an alkoxyl group, at least one of said Y, and Y, having been substituted by a group other than a hydrogen atom; R,, R,, and R each represents an alkyl group, a substituted alkyl group, or an aryl group; R, and R,, each represents an alkyl group; R,, represents a hydrogen atom, an alkyl group, and a group which together with R, and R, forms an alkylene linkage; X, represents an anion; and p is 0 or I (when p is 0, the compound forms an intramolecular compound) and at least one carbocyanine dye represented by the general formula II (H) wherein R, and R, each represents an alkyl group, a substituted alkyl group, or an aryl group; R represents a hydrogen atom, a methyl group or an ethyl group; Z, and Z, each represents nonmetallic atoms necessary for completing a benzoxazole nucleus, a naphthoxazole nucleus, a benzothiazole nucleus, a thiazole nucleus, a benzimidazolc nucleus, a naphthoimidazole nucleus, a benzselenazole nucleus, or a selehazole nucleus; X, represents an anion; and q represents 0 or 1 (when q is 0, the compound forms an intrarnolecular compound).

Illustrative of the alkyl or substituted alkyl group represented by R R R R and R in general formulas l and ll, there are a methyl group, an ethyl group, a propyl group, a Z-hydroxyethyl group, a Z-methoxyethyl group, a carboxymethyl group, a Z-carboxyethyl group, a 3-carboxypropyl group, a 4-carboxybutyl group, a Z-suIfoethyl group, a 3-sulfopropyl group, a carboethoxyethyl group, an aralkyl group (i.e., a phenyl methyl group), and an allyl group (i.e., a vinyl methyl group}. Also, the heteronucleus containing Z and Z may have been substituted by an alkyl group, a hydroxyl group, an alkoxyl group, an aryl group or a halogen atom.

The main feature in the chemical structure of the compound represented by general forrnula l is that the indolenine nucleus has been substituted by Y or Y,, that is, at least it has been substituted by a halogen atom, an alkyl group or an alkoxyl group. By the introduction of the aforesaid substituent, the color sensitivity of a silver halide emulsion can be increased. For example, the addition of the compound represented by general formula I, wherein Y, is H and Y is CH to a silver halide emulsion increases the spectral sensitivity 1.4 times that of the case where a compound having general formula I in which Y and Y; are H.

Also, by the addition of a carbocyanine dye of this invention to a silver halide emulsion, the sensitizing wave length region can be broadened to become sensitive over a green region of 500 mp. to 600mg. which is an object of this invention. Therefore, the carbocyanine dye represented by general formula I is effective to increase the super-sensitizing power and to obtain a highly green-sensitive silver halide emulsion.

The sensitizing dye represented by general formula ll can sensitize a silver halide emulsion in the green region, or over a region from the green region to the red region, the maximum wave length that can be sensitized by the sensitizing dye being about up to 670 mu.

Thus, by using the carbocyanine dye represented by general formula I together with the carbocyanine dye represented by general formula ll, the objects of this invention can be achieved, that is, the green sensitive region of the silver halide emulsion can be super-sensitized without substantially varying the maximum sensitizing wave length or while shifting the maximum sensitizing wave length to a shorter wave length side.

Furthermore, a silver halide emulsion produced in accordance with the present invention in which a sensitizing dye represented by general formula I is employed with a sensitizing dye represented by general formula ll which is capable of spectrally sensitizing only the green region can be particularly effective for producing a highly green-sensitive emulsion layer.

The sensitizing dyes used in this invention can be dissolved in organic solvents, such as, methanol, ethanol, acetone, and pyridine, and they may be incorporated in a silver halide emulsion together, or separately as solutions of the aforesaid solvents. The order of the: addition of the sensitizing dyes, the ratio of the amounts of sensitizing dyes, and the ratio of sensitizing dye to silver halide emulsion must be properly selected to yield the desired results.

To the silver halide emulsion containing the aforesaid sensitizing dyes of this invention, there may be added stabilizers antifoggants, hardening agents, wetting agents, plasticizers, and the like. In the case of a color photographic silver halide emulsion, a magenta coupler is usually also incorporated therein. The photographic silver halide emulsion thus supersensitized may be applied to a support such as a cellulose derivative film, a plastic film, and a baryta paper and the like.

Typical examples of sensitizing dyes represented by general formulas l and ll which are used in the present invention are shown below, but these particular examples are to be taken as merely representative of the dyes contemplated.

in a solution of 40 ml. of nitrobenzene and 3 ml. of acetic anhydride, there was heated for 5 minutes, under refluxing, 2.5 g. of 2-(B-anilinovinyl)-l,3,3,5-tetramethyl-3H-indolenium iodide. The solution prepared was mixed with 2 g. of anhydro-5 ti-dichlorol -ethyl-2-methyl-3-( 3-sulfopropyl) benzimidazolium hydroxide and 2.5 ml. of triethylamine. The resulting solution was heated for 5 minutes, under refluxing, to g. the reaction. After cooling, excessive ether was added to the solution to precipitate the dye. The crude crystals thus fonned were washed with water and recrystallized from a mixed solvent of methanol and isopropanol to provide a dye having a melting point of 226 C. The yield thereof was l.l g., and the maximum spectral adsorption in methanol was 508 ms.

The present invention will be further explained by the following examples.

To l00 g. of silver iodo-bromide emulsion prepared by conventional methods, there was added a mixture of a preselected amount of a methanol solution of the dye represented by general formula 1, and a preselected amount of a methanol solution of the dye represented by general formula II. The resulting emulsion was allowed to stand for 10 minutes at 37 C. and thereafter uniformly applied to a glass plate at a thickness of 7.0 ml. of the emulsion per cabinet size. The coated glass plates were then dried.

A light source of 5,400 K. temperature was obtained by passing a light 2,666 K. temperature through a DC transformation filter. The light-sensitive emulsion later formed above was exposed through an optical wedge using a yellow filter transmitting light having a wave length longer than about 500 mg, a red filter transmitting light longer than about 600 mp, and using no filter.

The light sensitive emulsion layer thus exposed was developed in a developer having the following composition for 10 minutes at 20 C.

Water 750 ml Sodium sulfite (anhydrous) I00 g.

Metal 2 g.

Hydroquinone S g.

Borax 2 g.

Further water to make L000 ml pH 8.7010. ID

The emulsion layer developed was processed in a stopping bath and a fixing bath and washed with water to provide a series of strips. The sensitivities of the areas exposed using no filter (called white sensitivity) using the yellow filter and using 0 the red filter were measured. By correcting the three kinds of CgHs CH3 CH3 5 1 sensitivities by uslng the energy distribution of the light source and the transmission power and the filters, a green sensitivity, 01 that is, sensitivity in the region of 500-600 mg, and a red sen- GH=CH CH= sitivity, that is, sensitivity in the region of 600-680 mg were 01 N 5 5 obtained. The optical density in the case of measuring the sensitivity was 01 (cf.; JIS K7609-l956). C1HsSOa' V A 019 Q5) The results thus obtained are shown in the following table.

Maximum Relative sensitivity sensitizing sensitizing dye amount sensitizing dye amount wave length, Example (ml.) (molar concentration) (ml.) (molar concentration) Red Green Fog mu 1 IIA (4x10-*) 2 I 0 (4x10 16.6 6.2 0.10 4 16.0 10.8 0.14 650 8 14.4 6.2 0.24 4 16.6 18.8 0.21 645 4 17.9 24.9 0.18 646 4.4 15.8 0.10 6.4 23.4 0.10 605 2 IIB (4x10 2 I E (4x10 17.4 6.5 0.10 4 18.0 0.8 0.11 643 4 2 18.0 10.7 0.10 640 4 4 17.5 20.5 0.10 686 2 10.4 0.12 4 16.5 0.11 550 3 IIC 4x10 2 II) 4 10- 3.11 34.0 0.12 4 X 14.6 37.8 0.13 630 4 2 13.1 38.6 0.18 4 4 14.6 30.3 0.12 630 2 16.8 0.10 4 20.6 0.10 565 Maximum Relative sensitivity sensitizing sensitizing dye amount sensitizingdye amount wave length,

Example (ml.) (molsroonoentration) (ml.) (molar concentration) Red Green Fog mu 4 IID 4 10- 2 IA 4x10 15.0 24.1 0.08 4 5. 6 23. 7 0.08 610 6 II E (ZXUH) 4 IA 10- 23.2 0.11 590 8 24. 9 0. 13 a 6 II F (BXIO- 2 I 0 (4X10-) 80.4 0.10 550 4 39.4 0. 11

7 II G 01x10) 2 I B (axis- 20,7 0.05 581 4 25.4 0.09 4 26.4 0.21 573 graphic silver halide emulsion a combination of the two kinds of sensitizing dyes, the green sensitivity can be increased without substantially reducing the red sensitivity thereof. Moreover, by using a combination of a sensitizing dye represented by general formula I and a sensitizing dye having a spectral sensitivity at a green region, an extremely high green sensitivity can be obtained.

What is claimed is:

l. A photographic silver halide emulsion containing at least one carbocyanine dye represented by the general formula wherein Y and Y, each represents a member selected from the group consisting of a hydrogen atom and a halogen atom; Y, and Y at least one of which is a group other than a hydrogen atom, each represents a member selected from the group consisting of a hydrogen atom, an allryl group, a halogen atom, and alkoxy group; R,, R,. and R each represents a member selected from the group consisting of an alltyl group, a substituted alkyl group selected from the class consisting of a hydroxyalkyl, an alkoxyalkyl, a carboxyalkyl, a sulfoalkyl a carboalkoxyalkyl group, an aralkyl and an ally] group, and an aryl group; R and R each represents an alkyl group; R represents a member selected from the group consisting of a hydrogen atom, an alkyl group, and a group which together with R, or R fonns an aikylene linkage; X, represents an anion; and p represents 0 or 1; said dye forming an intramolecular salt when p is 0, and at least one carbocyanine dye represented by general formula ll wherein R and R each represents a member selected from the group consisting of an alkyl group, a substituted alkyl group selected from the class consisting of a hydroxyalkyl, an alkoxyalkyl, a carboxyalkyl, a sulfoalkyl, a carboalkoxyalkyl group, an aralkyl and an allyl group, and an aryl group; R represents a member selected from the group consisting of a hydrogen atom, a methyl group and an ethyl group; Z, and 2,, represent nonmetallic atoms necessary for completing a nucleus selected from the group consisting of a benzoxazole nucleus, a naphthoxazole nucleus, at benzothiazole nucleus, a thiazole nucleus, a benzimidazole nucleus, a

naphthtoimidazole nucleus, a benzselenazole nucleus, and a selenazole nucleus; X represents an anion; and q represents 0 or i; said dye forming an intramolecular salt when q is O.

The above results show that by incorporating in a photo- 3 ,628 ,964 9 ,10 and at least one carbocyanine dye selected from the group /s\ tin of consls g CH=JJ CH=C aHe 8 0 A03 S OQNB f SON 

2. A photographic silver halide emulsion as claimed in claim 1 wherein the substituted alkyl group is selected from the class consisting of a 2-hydroxyethyl, a 2-methoxyethyl, a carboxymethyl, a 2-carboxyethyl, a 3-carboxypropyl, a 4-carboxybutyl, a 2-sulfoethyl, a 3-sulfopropyl, a carboethoxyethyl, a phenyl methyl and a vinylmethyl group.
 3. A photographic silver halide emulsion containing at least one carbocyanine dye selected from the group consisting of: 